I'm recently encouraged by and curious about the role of "behavioral engineering" in product design and conversion funnels. I like Nir and think he's on to something. http://www.nirandfar.com/2012/03/how-to-manufacture-desire.html

I'm not sure we as product developers want to addict our users.

Delight our users, yes.

But addiction? On the surface it seems bad because we don't want to be like drug dealers.